I. Field of the Invention
The present invention relates generally to conveyor systems and, more particularly, to a roller conveyor system.
II. Description of the Prior Art
There are a number of previously known roller conveyor systems having an elongated frame with a plurality of spaced and parallel rollers rotatably secured to the frame and defining an elongated conveyor track. The rollers typically are rotatably driven in the same direction of rotation and thus propel articles or workpieces positioned upon the track along the track in a predetermined direction.
In one type of previously known roller conveyor system, the workpieces positioned upon the conveyor track are sequentially stopped at work stations at predetermined longitudinally spaced positions along the track. A work stop means is associated with each work station to temporarily hold the workpiece at the work station. While the workpiece is held at the work station a machine, inspection or other type of operation can be performed on the workpiece. When the operation on the workpiece is completed, the work stop means releases the workpiece so that it can proceed to the next work station for the next machine, inspection or other operation. Simultaneously, of course, the work station prepares to receive another workpiece from the work station immediately upstream from it and this process is continuously repeated.
In the previously known roller conveyors of this latter type, the rollers are conventionally rotatably mounted to a drive shaft which in turn is rotatably mounted to the conveyor frame. The drive shaft for each roller along the conveyor is continuously rotatably driven by a conventional motor means but only a frictional drive connection is provided between each drive shaft and its associated roller. Each roller is normally rotatably driven by its associated drive shaft. Due to the friction drive between the roller and its drive shaft, however, the roller can remain stationary despite the continued rotation of the drive shaft. This arrangement is necessary to enable the workpieces to be temporarily halted at the various work stations along the conveyor track during the machining, inspection or other type of operation. Once the operation has been completed, the work stops are moved away from the workpiece at the work station and the rollers at the work station again begin to rotate due to the frictional drive connection between each roller and its drive shaft.
This previously known conveyor system, however, is disadvantageous in that, once stopped, the workpiece accelerates relatively slowly towards the next work station after the work stops have been removed. The slow acceleration of the workpieces from one work station and to the next work station is due to the frictional drive arrangement between each drive shaft and its roller.